| Summary: | 碩士 === 國立中正大學 === 化學工程所 === 93 === Photocatalyst products have become the leading commercial products in nanotechnology. When titanium oxide (TiO2) surfaces are irradiated, the hydroxyl radical (OH‧) formed by hole transfer in aqueous solution, as well as superoxide radical (O2-) produced from oxygen. These active species provide the oxidative activity for the degradation of organic and inorganic molecules in air and water. In this research, we combined the titanium oxide and biological recognition molecule to form a novel bio-photocatalyst for biomedical application. Nanoparticles of titanium oxide was modified by reacting with meso-2,3-dimercaptosuccinic acid (DMSA) to yield thiol groups, which were then activated for the coupling of tumor-targeting legand, a RGD-containing peptide (CDCRGDCFC), via the disulfide-bond linkage. Being incubated with cell lines derived from tumors, HepG2/C3A and HeLa cells, the titanium oxide particles bound with tumor-targeting peptide could adsorb specifically on the surface of cancer cells. Under a UV illumination, the ligand-bound titanium oxide became cytotoxic and could disrupt and damage the cancer cells. The surface modification of titanium oxide by DMSA was examined by measuring the change of zeta potential in the negative direction. More high the DMSA concentration more negative the zeta potential of the modified nanoparticles. The DMSA-modified TiO2 remained photocatalytic active using methylene blue as the substrate. However, due to a possible steric hindrance, the catalysis by modified TiO2 particles was delayed to some extent by the present of bound DMSA molecules on the surface. The cysteine residue on the RGD-containing peptide-bound titanium oxide could interact to fluorescent compound 5-IAF to form a covalent linkage. This fluorescently-labeled titanium oxide nanoparticles were observed in a fluorescence microsacope, suggesting the success in the coupling of RGD-containing peptide. Experimental data confirmed that the RGD-containing peptide-bound titanium oxide led higher dead rates of HepG2/C3A and HeLa cells, in comparison with intact titanium oxide. It caused HeLa cells to death more effectively than HepG2/C3A.
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